Add separate util class

Signed-off-by: TheKodeToad <TheKodeToad@proton.me>

libraries/launcher/org/prismlauncher/utils/UrlUtils.java

@@ -0,0 +1,121 @@
+// SPDX-License-Identifier: GPL-3.0-only
+/*
+ *  Prism Launcher - Minecraft Launcher
+ *  Copyright (C) 2022 TheKodeToad <TheKodeToad@proton.me>
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, version 3.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  Linking this library statically or dynamically with other modules is
+ *  making a combined work based on this library. Thus, the terms and
+ *  conditions of the GNU General Public License cover the whole
+ *  combination.
+ *
+ *  As a special exception, the copyright holders of this library give
+ *  you permission to link this library with independent modules to
+ *  produce an executable, regardless of the license terms of these
+ *  independent modules, and to copy and distribute the resulting
+ *  executable under terms of your choice, provided that you also meet,
+ *  for each linked independent module, the terms and conditions of the
+ *  license of that module. An independent module is a module which is
+ *  not derived from or based on this library. If you modify this
+ *  library, you may extend this exception to your version of the
+ *  library, but you are not obliged to do so. If you do not wish to do
+ *  so, delete this exception statement from your version.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package org.prismlauncher.utils;
+
+import java.io.IOException;
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import java.lang.reflect.Method;
+import java.net.Proxy;
+import java.net.URL;
+import java.net.URLConnection;
+import java.net.URLStreamHandler;
+
+import org.prismlauncher.utils.logging.Log;
+
+/**
+ * A utility class for URLs which uses reflection to access hidden methods.
+ * Unfortunately not supported on newer Java versions.
+ */
+public class UrlUtils {
+
+    private static URLStreamHandler http;
+    private static MethodHandle openConnection;
+    private static MethodHandle openConnectionProxied;
+
+    static {
+        try {
+            // invoke URL.getURLStreamHandler to obtain some of the default handlers before
+            // they are overridden
+            Method getURLStreamHandler = URL.class.getDeclaredMethod("getURLStreamHandler", String.class);
+            getURLStreamHandler.setAccessible(true);
+            http = (URLStreamHandler) getURLStreamHandler.invoke(null, "http");
+
+            // reflection is required due to not having access
+            // unreflect is used due to the potential frequency of calls
+            Method openConnectionReflect = URLStreamHandler.class.getDeclaredMethod("openConnection", URL.class);
+            openConnectionReflect.setAccessible(true);
+            openConnection = MethodHandles.lookup().unreflect(openConnectionReflect);
+
+            // a second method which takes in a proxy is required for a fully-functional
+            // URLStreamHandler
+            Method openConnectionReflectProxied = URLStreamHandler.class.getDeclaredMethod("openConnection", URL.class,
+                    Proxy.class);
+            openConnectionReflectProxied.setAccessible(true);
+            openConnectionProxied = MethodHandles.lookup().unreflect(openConnectionReflectProxied);
+        } catch (Throwable e) {
+            Log.error("URL reflection failed - some features may not work", e);
+        }
+    }
+
+    /**
+     * Determines whether all the features of this class are available.
+     *
+     * @return <code>true</code> if all features can be used
+     */
+    public static boolean isSupported() {
+        return http != null && openConnection != null && openConnectionProxied != null;
+    }
+
+    public static URLConnection openHttpConnection(URL url) throws IOException {
+        return openConnection(http, url);
+    }
+
+    public static URLConnection openHttpConnection(URL url, Proxy proxy) throws IOException {
+        return openConnection(http, url, proxy);
+    }
+
+    public static URLConnection openConnection(URLStreamHandler handler, URL url) throws IOException {
+        try {
+            return (URLConnection) openConnection.invokeExact(handler, url);
+        } catch (IOException | Error | RuntimeException e) {
+            throw e; // rethrow if possible
+        } catch (Throwable e) {
+            throw new Error(e); // otherwise, wrap in Error
+        }
+    }
+
+    public static URLConnection openConnection(URLStreamHandler handler, URL url, Proxy proxy) throws IOException {
+        try {
+            return (URLConnection) openConnectionProxied.invokeExact(handler, url, proxy);
+        } catch (IOException | Error | RuntimeException e) {
+            throw e;
+        } catch (Throwable e) {
+            throw new Error(e);
+        }
+    }
+
+}